As illustrated in FIG. 8, there are certain motor vehicles having the following disposed therein: an engine 202; an automatic transmission 204 having, for example, three different speed changes or gears, the transmission 204 being connected to the engine 202; and an air-conditioning unit (A/C) 206 driven by the engine 202. The air-conditioning unit 206 is provided with a compressor 208.
The transmission 204 is provided with a torque converter 210, a first solenoid (SOL1) 212, and a second solenoid (SOL2) 214, both of these solenoids providing speed or gear change control. The first and second solenoids 212, 214 are actuated by a control unit (ECU) 216 so as to execute speed or gear change control. The control unit 216 includes a mode timer table-selecting circuit 218. In addition, the control unit 216 communicates, for example electronically, with: an air conditioner switch 220 for detecting an on or off state of the air-conditioning unit 206, specifically an on or off state of the compressor 208; a throttle opening sensor 222 for detecting the degree of throttle opening; an engine speed sensor 224 for detecting engine speed determined by the number of engine revolutions; and a vehicle velocity sensor 226 for detecting vehicle velocity. Further, when gear shifting of the transmission 204 is decided, or when a downshift or kick-down, for example from a third drive gear D3 to a second drive gear D2, is decided, then the control unit 216 sets a speed change resumption-prohibiting time T6 (see FIG. 14) to preclude other gear shifting during the aforesaid decided act of gear shifting. Then, the control unit 216 selects one of an air conditioner-off-mode timer table (see FIG. 12) and an air conditioner-on-mode timer table (see FIG. 13), depending on whether the air-conditioning unit 206 is in an on or off state. The transmission 204 is thereby actuated and controlled, i.e., an on-time of the first solenoid 212 is controlled, and then a rev-up state of an engine speed is controlled. In short, when the kick-down (downshift) occurs, which is an act of gear shifting from one gear to a lower gear, for example drive gear D3 to drive gear D2, then the control unit 216 executes timer control in which a first speed or gear selection in transmission 204 (a neutral state) is provided substantially midway therebetween in order to promote an increase in the engine speed (FIG. 10).
However, for conventional automatic transmission controllers, even when the above-mentioned conventional timer control is effected after the decision to downshift from drive gear D3 to drive gear D2 as previously mentioned, desired timer values cannot be selected in spite of the fact that a rev-up speed of the engine speed varies depending on whether the air-conditioning unit 206 is in an on or off state (more specifically whether the compressor 208 is on or off). As a result, a timer value mismatch (an improper combination) causes either an excessive rev-up or an insufficient rev-up of the engine speed. This brings about inconveniences of non-smooth gear shifting and heavy shocks associated with such non-smooth shifting.
Details on the above will now be explained with reference to the drawings. As can be seen from the FIG. 9 chart showing the relationship between solenoid signals and gear positions, the control unit 216 causes both of the first and second solenoids 212, 214 to be powered on (electrically conducting) at a stage of the first speed or gear (1st). At a stage of a second speed or gear (2nd), the first solenoid 212 is off (not electrically conducting), while the second solenoid 214 is on (electrically conducting). At a stage of a third speed or gear (3rd), both of the solenoids are off (not electrically conducting).
As illustrated in the FIG. 10 timing diagram, when the kick-down from drive gear D3 to drive gear D2 occurs, the control unit 216 provides the timer control to retain a rev-up time of the engine speed in response to the output of solenoid signals by way of drive D1, where D1 is neutral, (the first speed is a neutral state and is operated by the aid of a one-way clutch) being interposed substantially midway between the gear shifting from D3 to D2. This is to put the automatic transmission 204 into neutral state because a rapid increase in the engine speed is hindered by the transmission mass that acts as an inertial force or drag. Conversely, there is another method in which the engine speed is increased by way of downshift followed by a back drive thereof from the rotational force from tires and inertial force of the vehicle. However, the back drive method cannot be employed because shocks are generated as is in the case with engine braking. In a drive range (D range), in view of a structure of the transmission 204, a neutral state cannot be reached, but at the first speed rotational power of the engine is transmitted to the tires through the one-way clutch in the transmission. As a result, the back drive from the tires is intercepted by the one-way clutch and prevented from being conducted to an engine. Shocks caused by engine braking are eliminated. In addition, the one-way clutch rotates faster on the side thereof connected to the tires, and is left released from the inertial force created by the transmission mass. That is, gears may be once shifted to a speed change stage at which rotational power is transmitted through the one-way clutch. The speed change stage is lower in speed than a speed change stage after the kick-down.
As can be seen from FIG. 11, for execution of the aforesaid timer control, when the kick-down or gear shifting from drive gear D3 to drive gear D2 occurs (step 302), it is then determined whether or not the compressor 208 of the air-conditioning unit 206 is on (step 304). When the compressor 208 is off, and thus the determination of step 304 is "NO", then the timer control is executed in accordance with the air conditioner-off-mode timer table, FIG. 12 (step 306). Meanwhile, when the compressor 208 is on, and thus the determination of step 304 is "YES", then the timer control is executed in accordance with the air conditioner-on-mode timer table, FIG. 13 (step 308). In addition, as illustrated in FIG. 14, while the timer control is executed, speed change resumption-prohibiting time T6 is set, which excludes other gear shifting acts in the course of the aforesaid decided act of gear shifting.
More specifically, when the compressor 208 is off, then no rotation is imparted to the compressor 208 with a significant load thereon (an off-state of the air conditioner switch 220), and then the rev-up of the engine speed is faster. In this case, as illustrated in FIG. 12, timer data in the air conditioner-off-mode timer table is selected. Then, the on-time of the first solenoid 212 is controlled so as to be shorter, and an acceptable extent of the rev-up of the engine speed is made smaller. Meanwhile, when the compressor 208 is on, then rotation is imparted to the compressor 208 with a significant load being exerted thereon (an on-state of the air conditioner switch 220), and then the rev-up of the engine speed is slower. In the on-state of the air conditioner switch, as illustrated in FIG. 13, timer data in the air conditioner-on-mode timer table is selected. Then, the on-time of the first solenoid 212 is controlled so as to be longer, and an allowable extent of the rev-up of the engine speed is made greater.
For the above reason, the mode timer tables are forced into proper use, depending on different characteristics of the rev-up of the engine speed. More specifically, the mode timer tables must properly be used from the standpoint of an increasing rate of the engine speed is less because of the load of the compressor 208, and the further standpoint of the load of the compressor 208 causes the engine speed (the number of rotation at the beginning of the increase) to be lower than when the compressor 208 experiences no load.
However, even when the control unit 216 is provided with such timer control logic as shown in FIG. 11, enhancement in engine output occurs when a throttle opening degree (THR) exceeds a compressor-out-of-operation-specified opening degree. Thus, a control is executed to cut (stop) the compressor 208 from being driven for a predetermined period of time, e.g. only ten seconds, immediately after the throttle opening degree (THR) recognizes the compressor-out-of-operation-specified opening degree. Consequently, the air-conditioning unit 206 appears off to the control unit 216; however, as a matter of fact, it does not mean that the load of the compressor 208 reaches zero upon switch-off of the air-conditioning unit 206. This means that the load of the compressor 208 is left for a certain period of time and reduces the rate of increase of engine speed. Accordingly, although the air conditioner-on-mode timer table (FIG. 13) should be selected as a mode timer table, an actual selection is made to the air conditioner-off-mode timer table (FIG. 12). The air conditioner-off-mode timer table is selected because the air conditioning compressor 208 is powered off substantially simultaneously with a speed change judgment (downshift or kick-down) despite the air-conditioning unit 206 being actually on, i.e. the compressor is stopped (cut) for the predetermined period of time, see FIG. 14 at 249. This causes inconveniences in that the rev-up time of the engine speed is insufficient, and thus gear shifting-caused shocks occur to a greater degree (FIG. 14). The G-waveform 250 at the front and rear of the vehicle has an unmatched engine speed which produces heavy pulling shocks because of the engine braking effect even though the acceleration pedal is pressed for increasing the engine speed. More specifically, when the kick-down or down shift occurs, then control is executed to power off the compressor 208 for some ten seconds in order to increase the engine speed at a faster rate. In order to select this timer mode table, switch-on/off of the compressor 208 is monitored at about twenty second intervals.